Cardiovascular System

1. Cardiovascular System Blood Physiology

2. What does blood do? • Transportation - gases, nutrients, waste • Regulation - pH, temperature, water levels • Protection - clotting, immunity, phagocytosis

3. Physical Characteristics • Temp = 100.4 ° F • pH = 7.35-7.45 • Volume = 5-6 L (male), 4-5 L (female) • Viscosity = more viscous than water • Red color (oxygenated)

4. Blood components • Plasma - fluid matrix • Formed elements: • Erythrocytes (RBCs) • Platelets • Leukocytes (WBCs) - Neutrophils, Lymphocytes, Monocytes, Eosinophils, Basophils

6. Hemopoiesis • Red bone marrow • Pluripotent stem cells - can develop into several different types • Myeloid and lymphoid stem cells • “Blasts” - precursors to specific types • Directed by chemical signals (hormones)

8. Erythrocytes • Anatomy: • Biconcave • No nucleus or organelles • Flexible membrane • Physiology: • Oxygen transport • Carbon dioxide transport

9. Erythropoiesis • Pluripotent  Myeloid  Colony forming unit (CFU-E) Proerythroblast • Reticulocyte - ejects nucleus and passes into bloodstream • Mature in 1 to 2 days • Erythropoietin (EPO) produced by kidneys

10. Control of Erythropoiesis • Usually Erythropoiesis = RBC Destruction • Negative feedback • Hypoxia  kidneys release more EPO • Proerythroblasts mature more rapidly • More RBCs = Greater oxygen-carrying capacity (including to kidneys) • Kidneys stop releasing EPO

11. Hemoglobin • 280 million molecules per RBC • Components: • Globin - protein w/ four chains • Heme - Fe2+ at center binds to O2 (one heme per chain = 4 O2 per molecule) • B12 also needed

12. Anemia • Reduced oxygen-carrying capacity • Types: • Iron-deficient anemia - most common • Megaloblastic anemia • Pernicious anemia • Hemorrhagic anemia • Hemolytic anemia • Thalassemia • Aplastic anemia • Sickle-cell disease

13. Leukocytes • WBCs • Myeloid stem cells  all except lymphocytes • Lymphoid stem cells  finish development in lymphatic tissues • Cytokines (CSFs and Interleukins)

14. Types • Neutrophils (60-70%) - phagocytosis of bacteria • Lymphocytes (20-25%) • B cells - antibody secretion • T cells - attack viruses • Monocytes (3-8%) - phagocytosis as macrophages

15. Types (cont.) • Eosinophils (2-4%) – allergic reactions; phagocytize parasitic worms • Basophils (0.5-1%) - intensify inflammatory response • Differential WBC count can indicate infection, allergic reactions, blood disorders, etc. when percentages vary from normal • Leukemia

16. Platelets • Thrombopoeietin causes myeloid stem cells  megakaryoblasts  megakaryocytes  splinter into platelets (thrombocyte) • 150,000-400,000 per uL • Form plugs in damaged vessels • Release clotting factors

17. Hemostasis • Sequence of responses that stops bleeding (possible hemorrhage) • Mechanisms: • Vascular spasm • Platelet plug formation • Blood clotting (Coagulation)

18. Vascular Spasm • Immediate contraction of smooth muscle in arteries and arterioles • Reduces blood loss - allows time for other mechanisms to start

19. Platelet Plug Formation

20. Platelet Plug Formation

21. Platelet Plug Formation

22. Clotting (Coagulation) • Clot = gel formed from formed elements trapped in fibrin threads • Cascade of reactions involving sequence of clotting factors (Ca2+, enzymes from liver, vitamin K derivatives) • Thrombosis/Hemorrhage • Hemophilia • Anticoagulants

23. ABO Blood Groups

24. Heart Physiology

29. Heart Valves • Atrioventricular valves • Connected to papillary muscles by chordae tendinae • Ventricles relax, chordae are slack, valve opens due to pressure from atria • Chordae prevent backflow • Semilunar valves • Opened by ventricular pressure • Backflow fills cusps and closes valves

31. Coronary Circulation • Nutrients cannot diffuse easily to myocardium from chambers • Coronary arteries branch from aorta • Coronary veins empty into sinus and then to right atrium

33. Histology of Cardiac Muscle

34. Action Potentials in Cardiac Muscle • Depolarization - Voltage-gated fast Na+ channels open - rapid depolarization • Plateau - sustained depolarization due to Ca2+ inflow balancing K+ outflow • Repolarization - Ca2+ channels close, K+ channels open

35. Action Potentials in Cardiac Muscle

36. Conduction System • Autorhythmic fibers repeatedly and rhythmically generate action potentials • SA node spontaneously depolarizes (pacemaker potential) - potential spreads to both atria • SA nodeAV nodeAV bundleBundle branchesPurkinje fibers

37. Conduction System

38. Blood Flow

39. Electrocardiogram • P wave = atrial depolarization • QRS complex = rapid ventricular depolarization • T wave = ventricular repolarization

40. Cardiac Cycle • Atrial Systole • Ventricular Systole • Relaxation • What events happen during each stage?

41. Heart Sounds • Auscultation • Blood turbulence caused by valves closing • S1 (“lubb”) = AV valves closing • S2 (“dupp”) = SL valves closing • Murmur - abnormal heart sounds, usually indicating valve disorders (such as stenosis or valve incompetence)

42. Cardiac Output • Blood volume (mL) ejected by left ventricle per minute • CO = SV x HR (mL/min = mL/beat x beats/min) • CO should equal venous return • SV of left vent. = SV of right vent. • Heart rate regulated by autonomic nervous system • Stroke volume regulated by strength of contraction and resistance in blood vessels

43. Arrhythmias • Abnormal rhythm due to defect in conduction system • Bradycardia - HR  50 bpm • Tachycardia - HR  100 bpm • Fibrillation - rapid and uncoordinated

44. Some specific arrhythmias • Heart block - pathway between atria and ventricles blocked (usually AV node) • 1st degree block - P-Q interval prolonged due to slow AV node conduction • 2nd degree block - fewer QRS complexes than P due to lost potentials between SA and AV (“dropped beats”) • 3rd degree block - no potentials through AV - chambers paced separately • Atrial flutter - rapid atrial contractions coupled w/ 2nd degree block

45. Some specific arrhythmias • Atrial fibrillation - atria at 300-600 bpm (no defined P waves) - irregular heart beat, reduced efficiency, stroke • Ventricular tachycardia - heart disease or recent infarct - low BP and heart failure • Ventricular fibrillation - ventricles “quiver” and stop pumping - no defined waves on ECG • Premature ventricular contraction - due to ectopic focus - can be benign (stress, stimulatants, etc)

46. Blood Vessels • Arteries  Arterioles  Capillaries  Venules  Veins • Three tunics: • Tunica interna (intima) - simple squamous (endothelium) • Tunica media - smooth muscle and elastic fibers - vasoconstriction/vasodilation • Tunica externa - elastic and collagen fibers

48. Venous Return • Caused by pressure from left ventricle • Decreased by increased pressure in right side of heart • Also due to: • Skeletal muscle pump • Respiratory pump (abdominal cavity pressure , thoracic cavity )

49. Capillaries • Single layer of endothelium and basement membrane • Exchange vessels • Microcirculation = flow from arterioles  capillaries  veins • Capillary bed = 10-100 capillary network (precapillary sphincters control flow)